Disk gangs of harrows are often resiliently supported on the harrow frame so that each gang can independently yield to obstructions met by the disks in the farmland being harrowed. This reduces the impact forces transmitted to the frame and the potential damage to the disk gang caused by engagement with obstructions such as rocks, stumps or roots.
Existing resilient mounting arrangements often include U-shaped spring members mounted between a cross member on the frame and the shaft on which the disks are mounted. These U-shanks or disk cushions are typically manufactured from square or rectangular cross-section material, formed to shape and heat-treated. U.S. Pat. Nos. 4,066,132 and 4,407,372 disclose U-shaped spring members having rectangular cross sections. In some cases these disk cushions may have one or two tapered legs, where the thickness of the leg is variable along its length. This is done to provide exactly the right spring rate to meet the application requirements.
Disk cushions undergo loading in many planes, often resulting in a torsional load being applied to the part, concentrated at the central portion of the U-shaped member between the leg portions. This applied torsion tends to be a repeated and cyclic load that often leads to failure of the part. The square shape of the part is not the optimum shape to resist this form of torsional fatigue. Therefore, there is a desire for a cushion with an improved resistance to torsional loads applied during use of the disk harrow.